A touch panel system is widely used in various electronic devices such as a PC (personal computer), a mobile terminal and a tablet.
In the touch panel system, when a user causes his/her finger or a touch pen to be in contact with a touch panel, input operation to the touch panel is performed. In a touch panel system of an electrostatic capacitance method, change in an electrostatic capacitance in a touch panel, which is caused when a finger of a user or a touch pen is in contact with the touch panel, is detected, and a position at which the change in the electrostatic capacitance is caused in the touch panel is recognized as an input position to the touch panel.
In recent years, various stylus pens such as an active stylus pen have been developed as touch pens having a function of outputting a signal. It has been expected to further enhance performance of a touch panel system by applying the stylus pens to the touch panel system.
PTL 1 discloses a touch panel system that when input operations are performed by a plurality of stylus pens (electronic pens) to a touch panel, individual touch positions are able to be detected accurately.